congresos y reuniones científicas
A new Carodnia-like Xenungulata (Mammalia) from the Paleogene from Patagonia, Argentina
BOND, M., GELFO,J.N.AND G.M.LÓPEZ
Congreso; III Congreso Latinoamericano de Paleontología de Vertebrados; 2008
Universidad Nacional del Comahue
Abstract: The Xenungulata are only known for scarce taxa from the Paleogene of several South American localities, asPatagonia (Carodnia feruglioi and Notoetayoa gargantuai), the brazilian locality of Itaboraí (Carodnia vierai) andColombia (Etayoa bacatensis). An unpublished taxa from Rio Loro Formation apparently also indicate their presenceat Northwestern Argentina. We preliminary describe a fragmentary right lower jaw with the partially preserved p4and m1 nearly complete (MLP 90-II-12-121). This remain came from Cerro Redondo, at the East of the ChubutProvince and was collected from the lower fossil horizon identified by Simpson (1935) and considered as probablystratigraphically equivalent or older than the Carodnia Zone , despite no common taxa were found between them.The m1 is well preserved, with the trigonid somewhat higher, wider and longer than the talonid. This tooth showsan almost labio-lingually oriented bilophodont structure characteristic of other Xenungulata and Pyrotheria. Theprotolohid is mesially concave, the cutting plane of the lophid is parallel to the one of the hypolophid, and bothare inclined distally. There is no trace of the paraconid. The metaconid could be distinguished from the protolophidby a strong enamel edge that bends at the lingual tip of the lophid. The protoconid is not so clearly distinguishedfrom their outline. A short metacristid descend mesio-labially from the metaconid almost reaching the lingual endof the paracristid. The paracristid abruptly descends mesio-lingually from the labial ends of the protolophid, andprogressively bends lingually, to the mesial base of the trigonid. In the hypoconid sector of the hypolophid, a smoothcristid obliqua descends up to the base of the distal wall of the trigonid near to the protoconid area. The entoconidcould be identified in the hypolophid by an enlargement at its lingual end. The new taxa here described differfrom Etayoidae due to the absence of paraconid and a more bilophodont tooth, being morphologically close toCarodniidae. But, in contrast to Carodnia, the new specimen presents a more primitive pattern with remnants ofthe trigonid structure mesial to the protolophid (metacristid and paracristid), a well marked cristid obliqua and thedevelopment of a short entocristid. These generalized characters seem to highlight Simpson (1935) observationthat Cerro Redondo lower level could be older than Carodnia Zone at Bajo de La Palangana.